Photoepilation (also known as light hair removal) is a non-surgical cosmetic procedure that uses intense light to remove unwanted hairs and slow down their regeneration. Light hair removal (including laser and IPL-Intense Pulsed Light) is the fastest growing non-surgical esthetic application.
Current approaches rely on the natural color (absorption) contrast between the hair and the skin to damage the hair by photo heating. They consequently fail for clear hairs (blond and white) and, even in the ideal configuration of dark hairs on clear skin; the required light intensities are responsible for local skin injuries that can become permanent. The less cost and frequency of the treatment are the factors behind the growth of the market.
A method for enhanced photoepilation was described in the patent application WO2013079105 in which plasmonic gold nanocomplexes are used to artificially enhance the absorption contrast between the hair and the skin. In this method cationic gold nanocomplexes able to accumulate at the hair cuticle and root levels are used. Those nanocomplexes present a strong surface plasmon resonance (SPR) in the near infrared and thus can be heated up very efficiently at wavelengths out of the melanin absorption spectrum. However, in practice, only a finite number of nanocomplexes will reach the hair cuticle/root, thus limiting the actual depilation efficiency, because the quantity of heat generated at the hair cuticle/root is directly proportional to the quantity of delivered nanocomplexes. In addition nanocomplexes belong to nanotechnologies and from a commercial/societal viewpoint, they may raise some issues related to tiny size like potential toxicity or clearance.
Thus, from what is known in the art, it is derived that the increase the amount of nanocomplexes reaching the targeted region and lift the issues related to the nanosize of the nanocomplexes while maintaining the photothermal properties of individual plasmonic nanoparticles is of great interest.